50 



BOTANY 



PART I 



attached to the roots of their host plants by means of disc-shaped 

 or wart-shaped haustoria. In extreme cases no subterranean roots 

 may be developed, and the parasite only bears haustoria which 

 penetrate the host (Cuscuta, Fig. 196 H)., The haustoria of the 

 Jiafflesiaceae traverse the body of the host -plant as elongated 

 filaments of cells, and are capable of regenerating the parasite. 

 The immense flowers of Rafflesin Arnoldi, which spring directly from 

 the roots of Cissus, originate from similar haustoria. The reduction 

 of the roots may extend to such a degree that, in a number of plants, 



Fig. 53. — Part of the shoot ot Selaginella Martensii with rhizophorcs. 

 (From GoEBEL, Organography. Nat. size.) 



no roots are formed. It has been already mentioned that in the 

 case of Coralliorrhiza innata (Fig. 24) the rhizome assumes all the 

 functions of the roots, which are entirely absent. Also in many 

 aquatic i)lants (Salvinia, IFolffia arrhba, Utrirularia, Ceratophjllum) 

 roots are altogether absent since these plants no longer require them. 

 The beard -like epiphytic Tillandsia usneoides, belonging to the 

 Bromeliaceae, has no roots and obtains the water it requires by means 

 of special scale-like hairs. 



Members of Independent Origin 



The existence of parts of the plant combining the characters of 

 distinct primary members, and to which an independent phylogenetic 

 origin must be ascribed, has been pointed out by Goebel (•''^). 



